Method and system for interest groups in a content centric network

ABSTRACT

One embodiment provides a system for facilitating efficient communication of an interest group packet indicating a collection of interests. During operation, the system receives, by an intermediate node, a first packet which has a name and indicates a set of member interests, wherein a member interest has a name, wherein a name is a hierarchically structured variable length identifier that includes contiguous name components ordered from a most general level to a most specific level. In response to obtaining a content object which satisfies a member interest, the system removes the indicated member interest from the first packet. The system adds an entry in a pending interest table for the first packet, wherein the entry indicates the name for the first packet, the name for each member interest, and an indicator of whether each member interest is satisfied. The system transmits the first packet to another node.

RELATED APPLICATION

The subject matter of this application is related to the subject matter in the following applications:

-   -   U.S. patent application Ser. No. 13/847,814, entitled         “ORDERED-ELEMENT NAMING FOR NAME-BASED PACKET FORWARDING,” by         inventor Ignacio Solis, filed 20 Mar. 2013 (hereinafter “U.S.         patent application Ser. No. 13/847,814”);     -   U.S. patent application Ser. No. 12/338,175, entitled         “CONTROLLING THE SPREAD OF INTERESTS AND CONTENT IN A CONTENT         CENTRIC NETWORK,” by inventors Van L. Jacobson and Diana K.         Smetters, filed 18 Dec. 2008 (hereinafter “U.S. patent         application Ser. No. 12/338,175”); and     -   U.S. patent application Ser. No. 14/231,515, entitled “AGGREGATE         SIGNING OF DATA IN CONTENT CENTRIC NETWORKING,” by inventors         Ersin Uzun, Marc E. Mosko, Michael F. Plass, and Glenn C. Scott,         filed 31 Mar. 2014 (hereinafter “U.S. patent application Ser.         No. 14/231,515”);         the disclosures of which are herein incorporated by reference in         their entirety.

BACKGROUND

Field

This disclosure is generally related to distribution of digital content. More specifically, this disclosure is related to a method and system for efficient communication of a collection of distinct interests.

Related Art

The proliferation of the Internet and e-commerce continues to create a vast amount of digital content. Content-centric network (CCN) architectures have been designed to facilitate accessing and processing such digital content. A CCN includes entities, or nodes, such as network clients, forwarders (e.g., routers), and content producers, which communicate with each other by sending an interest packet for content and receiving a content object packet (or a manifest) in return. A CCN interest and a content object (or a manifest) are identified by their unique names, which are typically hierarchically structured variable length identifiers (HSVLI). An HSVLI can include contiguous name components ordered from a most general level to a most specific level. A manifest is a content object which indicates a collection of “member” content objects based on a name for each member content object. A manifest can be represented in a tree-like topology, and a member content object can be a data object or another manifest. An entity in possession of a manifest can retrieve the member content objects by transmitting one interest for each member content object based on the indicated name. Manifests are described in U.S. patent application Ser. No. 14/231,515.

As an interest packet is routed through the network from a content requesting node to a content producing node, each intermediate CCN router adds an entry in its pending interest table (PIT) corresponding to the interest and forwards the interest to the next CCN router. When a matching content object packet is sent from the content producing node back to the requesting node, it follows the reverse path of the interest. Each intermediate CCN router forwards the content object along the requesting or arrival interfaces listed in the corresponding PIT entry, and subsequently removes the PIT entry, indicating that the interest has been fulfilled.

The current CCN protocol is based on a one-to-one symmetry. That is, one interest is used to retrieve one content object or manifest. However, when the names of multiple content objects are known a priori, or obtained from a manifest, a requesting consumer may realize an additional burden in sending one individual interest for each content object. Furthermore, each intermediate router stores one entry for each symmetrical interest and content object exchange. This may result in an inefficient system and decrease the effectiveness of data distribution in the network.

SUMMARY

One embodiment provides a system for facilitating efficient communication of an interest group packet indicating a collection of interests. During operation, the system receives, by an intermediate node, a first packet which has a name and indicates a set of member interests, wherein a member interest has a name, wherein a name is a hierarchically structured variable length identifier that includes contiguous name components ordered from a most general level to a most specific level. In response to obtaining a content object which satisfies a member interest, the system removes the indicated member interest from the first packet. The system adds an entry in a pending interest table for the first packet, wherein the entry indicates the name for the first packet, the name for each member interest, and an indicator of whether each member interest is satisfied. The system transmits the first packet to another node, thereby facilitating efficient communication of the set of member interests indicated in the first packet.

In some embodiments, the first packet further includes information associated with a condition for splitting the first packet into one or more individual interests, wherein an individual interest has a same name as a respective member interest of the first packet. The system processes the one or more individual interests.

In some embodiments, the information associated with the condition is a hop count which indicates a number of remaining hops until the first packet is to be split into the one or more individual interests. In response to determining that the hop count is equal to zero, the system splits the first packet into the one or more individual interests. The system discards the first packet, and forwards the one or more individual interests.

In some embodiments, the information associated with the condition is a name prefix. In response to determining that the name prefix matches an entry in a forwarding information base based on a longest prefix match, the system splits the first packet into the one or more individual interests, discards the first packet, and forwards the one or more individual interests.

In some embodiments, in processing an individual interest, the system performs a lookup in a cache for a matching content object based on a name for the individual interest. In response to obtaining the matching content object, the system forwards the matching content object to a previous-hop node, and removes from the pending interest table a matching entry, or removes from the matching entry an arrival interface associated with the individual interest. In response to not obtaining the matching content object, the system performs the following operations: the system performs a lookup in the pending interest table for the matching entry corresponding to the individual interest; in response to obtaining the matching entry, the system adds to the matching entry the arrival interface associated with the individual interest; in response to not obtaining the matching entry, the system adds a new entry corresponding to the individual interest; and the system forwards the individual interest.

In some embodiments, in response to obtaining a content object that satisfies a member interest, the system performs a lookup in the pending interest table for a matching entry corresponding to the first packet. In response to obtaining the matching entry, the system marks in the matching entry the indicator that the member interest is satisfied, and in response to determining that all member interests indicated in the matching entry are satisfied, the system removes the matching entry from the pending interest table. In response to not obtaining the matching entry, the system performs the following operations: in response to determining that one or more member interests are indicated in the first packet, the system adds the entry in the pending interest table for the first packet, wherein the added entry does not indicate the satisfied member interest, and the system forwards the first packet; and in response to determining that no member interests are indicated in the first packet, the system discards the first packet.

In some embodiments, in response to not obtaining a content object which satisfies a member interest, the system performs a lookup in the pending interest table for a matching entry corresponding to the first packet. In response to obtaining the matching entry, the system marks in the matching entry the indicator that the member interest is satisfied. In response to not obtaining the matching entry, the system adds the entry in the pending interest table for the first packet.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates an exemplary network that facilitates communication of an interest group packet indicating a collection of interests, in accordance with an embodiment of the present invention.

FIG. 1B illustrates an exemplary interest group packet, in accordance with an embodiment of the present invention.

FIG. 1C illustrates an exemplary interest group packet, in accordance with an embodiment of the present invention.

FIG. 1D illustrates an exemplary pending interest table maintained by an intermediate node, in accordance with an embodiment of the present invention.

FIG. 1E illustrates an exemplary pending interest table maintained by an intermediate node, in accordance with an embodiment of the present invention.

FIG. 1F illustrates an exemplary interest group packet, including information associated with a condition to split the interest group packet, in accordance with an embodiment of the present invention.

FIG. 1G illustrates exemplary interests created based on splitting the exemplary interest group packet of FIG. 1F, in accordance with an embodiment of the present invention.

FIG. 1H illustrates an exemplary pending interest table maintained by an intermediate node, in accordance with an embodiment of the present invention.

FIG. 1I illustrates an exemplary pending interest table maintained by an intermediate node, in accordance with an embodiment of the present invention.

FIG. 2 presents an exemplary table illustrating an exemplary interest group in Augmented Backus-Naur Form notation, in accordance with an embodiment of the present invention.

FIG. 3A presents a flow chart illustrating a method by an intermediate node for facilitating communication of an interest group packet indicating a collection of interests, in accordance with an embodiment of the present invention.

FIG. 3B presents a flow chart illustrating a method by an intermediate node for facilitating communication of an interest group packet indicating a collection of interests, in accordance with an embodiment of the present invention.

FIG. 4 presents a flow chart illustrating a method by an intermediate node for facilitating communication of an interest group packet indicating a collection of interests, including detection of information associated with a condition to split the interest group packet, in accordance with an embodiment of the present invention.

FIG. 5 illustrates an exemplary computer and communication system that facilitates communication of an interest group packet indicating a collection of interests, in accordance with an embodiment of the present invention.

In the figures, like reference numerals refer to the same figure elements.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Overview

Embodiments of the present invention provide a system which facilitates efficient communication and distribution of content based on an interest group, which is a CCN composite message that represents or indicates a collection of distinct interests. A current CCN protocol is based on a one-to-one symmetry for an interest and a content object. That is, a consumer generates and transmits one interest, and receives one responsive content object from a producer (and/or intermediate routers). Each entity that receives the interest performs a lookup in its cache or content store (CS) for the matching content object, and also performs a lookup in its pending interest table (PIT), to either add a new entry for the interest or add (or aggregate) an arrival interface for an existing entry. Each entity that receives the content object also performs a similar lookup in its CS, and also performs a lookup in its PIT, to remove an existing entry or to remove an arrival interface for an existing entry.

A recent construction, known as “interest lists,” proposes a type of CCN message which carries a collection of interests through the network. An interest list includes a name, just as an interest includes a name. Interest lists are described in Kurihara, et al., “List Interest: Packing Interests for Reduction of Router Workload in CCN 1.0.” A forwarder stores an interest list in its PIT based on the name for the interest list. Furthermore, a forwarder performs a lookup in its content store for each constituent interest. If a match is found in the CS, the forwarder transmits the individual content object. If a match is not found in the CS, the forwarder transmits the interest list based on forwarding information. An interest list is only dropped when all interests in the interest list are satisfied. Thus, an interest list representing n individual interests solicits n individual content object responses. However, because an interest list is forwarded as a single message, an interest list contains interests that are ultimately forwarded to the same destination, which can create inefficiencies. Furthermore, interest lists do not dynamically decompose as they traverse the network, which can lead to further inefficiencies.

Embodiments of the present invention solve these problems by introducing a new type of CCN message: an “interest group.” An interest group is similar to an interest list in that an interest group indicates a collection of “member” interests. However, an interest group also includes several key features not included in an interest list. First, an interest group can be truncated as it traverses the network. That is, an intermediate router can satisfy a member interest, and subsequently remove the indication of a satisfied member interest before forwarding the interest group onwards, as described below in relation to FIGS. 1B and 1C. Second, an interest group can indicate its member interests with names that are independent of the name for the interest group. Third, an interest group can include conditions which trigger an intermediate router to decompose its member interests. That is, interest group can be split into individual interests (or smaller interest groups or subsets of individual interests), where the individual interests match the member interests. For example, a trigger condition can occur upon reaching a pre-configured number of hops, or when an interest reaches a distinct topological portion of the network (e.g., an organizational boundary), as described below in relation to FIGS. 1F-1G.

Thus, the present system provides improvements to the distribution of digital content, where the improvements are fundamentally technological. Embodiments of the present invention provide a technological solution (e.g., using an interest group to transmit requests for digital content) to the technological problem of the efficient, secure, and effective distribution of digital content.

In CCN, each piece of content is individually named, and each piece of data is bound to a unique name that distinguishes the data from any other piece of data, such as other versions of the same data or data from other sources. This unique name allows a network device to request the data by disseminating a request or an interest that indicates the unique name, and can obtain the data independent from the data's storage location, network location, application, and means of transportation. The following terms are used to describe the CCN architecture:

Content Object (or “content object”): A single piece of named data, which is bound to a unique name. Content Objects are “persistent,” which means that a Content Object can move around within a computing device, or across different computing devices, but does not change. If any component of the Content Object changes, the entity that made the change creates a new Content Object that includes the updated content, and binds the new Content Object to a new unique name.

Unique Names: A name in a CCN is typically location independent and uniquely identifies a Content Object. A data-forwarding device can use the name or name prefix to forward a packet toward a network node that generates or stores the Content Object, regardless of a network address or physical location for the Content Object. In some embodiments, the name may be a hierarchically structured variable-length identifier (HSVLI). The HSVLI can be divided into several hierarchical components, which can be structured in various ways. For example, the individual name components parc, home, ccn, and test.txt can be structured in a left-oriented prefix-major fashion to form the name “/parc/home/ccn/test.txt.” Thus, the name “/parc/home/ccn” can be a “parent” or “prefix” of “/parc/home/ccn/test.txt.” Additional components can be used to distinguish between different versions of the content item, such as a collaborative document.

In some embodiments, the name can include a non-hierarchical identifier, such as a hash value that is derived from the Content Object's data (e.g., a checksum value) and/or from elements of the Content Object's name. A description of a hash-based name is described in U.S. patent application Ser. No. 13/847,814. A name can also be a flat label. Hereinafter, “name” is used to refer to any name for a piece of data in a name-data network, such as a hierarchical name or name prefix, a flat name, a fixed-length name, an arbitrary-length name, or a label (e.g., a Multiprotocol Label Switching (MPLS) label).

Interest (or “interest”): A packet that indicates a request for a piece of data, and includes a name (or a name prefix) for the piece of data. A data consumer can disseminate a request or Interest across an information-centric network, which CCN routers can propagate toward a storage device (e.g., a cache server) or a data producer that can provide the requested data to satisfy the request or Interest.

The methods disclosed herein are not limited to CCN networks and are applicable to other architectures as well. A description of a CCN architecture is described in U.S. patent application Ser. No. 12/338,175.

Exemplary Network and Communication

FIG. 1A illustrates an exemplary network 100 that facilitates communication of an interest group packet indicating a collection of interests, in accordance with an embodiment of the present invention. Network 100 can include a content requesting device 116, a content producing device 118, and a router or other forwarding device at nodes 102, 104, 106, 108, 110, 112, and 114. A node can be a computer system, an end-point representing users, and/or a device that can generate interests or originate content. A node can also be an edge router (e.g., CCN nodes 102 and 114) or a core router (e.g., intermediate CCN routers 104-112). Each CCN router can maintain a pending interest table (PIT) (e.g., PIT 130 of node 110) and a forwarding information base (FIB) (not shown). PIT 130 can include PIT entries 131.1-131.n associated with pending interests. A PIT entry (e.g., PIT entry 131.1) can include a name 132, member interest information 134, and incoming interfaces 136. Member interest information 134 can include member interest names 142.1-142.m and member indicators 144.1-144.m. For example, member indicator 144.1 is an indicator (such as a flag or bit) of whether the interest by the name of member interest name 142.1 has been satisfied.

During operation, node device 116 can send an interest group 150, where interest group 150 indicates a collection of interests for data. Interest group 150 is a packet that can include a basename 152 and member interest names 154.1-154.n corresponding to each member interest. Basename 152 is not required to be related to member interest names 154.1-154.p. In other words, member interest names 154.1-154.p can be independent of and distinct from basename 152. An exemplary interest group packet is described below in relation to FIG. 1B. Interest group 150 can travel through network 100. Node 110 can receive interest group 150 and can perform a lookup in its CS for a matching content object based on, e.g., member interest name 154.1. If no matching content object is found in the CS, node 110 can perform a lookup in PIT 130 for a matching PIT entry corresponding to interest group 150, based on basename 152. If no matching PIT entry is found, node 110 can add a PIT entry for interest group 150. An exemplary PIT is described below in relation to FIG. 1D. For example, the added PIT entry can include name 132 with a value of basename 152, member interest names 142.1-142.m corresponding to member interest names 154.1-154.p, and corresponding member indicators 144.1-144.m. For a newly added PIT entry, member indicators 144.1-144.m can be set to a default value of “0” or a value that indicates that the corresponding member interest is not satisfied. Node 110 can then forward interest group 150 to a next-hop node (such as node 108) based on information in its FIB. If a matching PIT entry is found, node 110 can add the arrival interface of interest group 150 to the matching PIT entry, and then forward interest group 150.

If a matching content object for a member interest is found in the CS, node 110 can remove the indication of the satisfied member interest from the interest group, as described below in relation to FIGS. 1B and 1C, and forward the matching content object on a reverse path (e.g., via nodes 114 and 102). Node 110 can perform a lookup in PIT 130 for a matching PIT entry corresponding to interest group 150, based on basename 152. If no matching PIT entry is found, and no remaining member interests are indicated in interest group 150, node 110 can discard interest group 150. If there are any remaining member interests indicated in interest group 150, node 110 can add a PIT entry for interest group 150. For example, the added PIT entry can include name 132 with a value of basename 152, member interest names 142.1-142.m corresponding to member interest names 154.1-154.p, and corresponding member indicators 144.1-144.m. Note that the added PIT entry will not include the indication of any satisfied member interests which are previously removed from interest group 150.

If a matching PIT entry is found, node 110 can mark the appropriate member indicator as satisfied, where the marked member indicator corresponds to the member interest name for the satisfied interest (e.g., mark as satisfied indicator 144.1 corresponding to member interest name 142.1, which has a value that is the same as member interest name 154.1). An exemplary PIT showing the marking of a member indicator for a satisfied member interest is described below in relation to FIG. 1E. If all of the member interests indicated in the matching PIT entry are satisfied, node 110 can remove the matching PIT entry from the PIT. A detailed description of these operations can be found below in relation to FIGS. 1B-1E, 3A, and 3B.

Thus, embodiments of the present invention provide an effective solution for enabling 1-to-n interest to content object retrieval, where an interest group indicates a collection of member interests, and where an intermediate router can remove a satisfied member interest from the interest group before forwarding the interest group on. Furthermore, an interest group can include a triggering condition which indicates to an intermediate router to split the interest group into its constituent member interests. Decomposition is described below in relation to FIG. 4.

Exemplary Interest Groups and PITs

FIG. 1B illustrates an exemplary interest group packet 150, in accordance with an embodiment of the present invention. Interest group packet 150 (or interest group 150) at a time of T1 can include a basename 152 with a value of “/basename” and member interest names 154.1-154.5. For example, member interest name 154.1 is “/a/b,” member interest name 154.2 is “/c/d,” member interest name 154.3 is “/e/f,” member interest name 154.4 is “/g/h,” and member interest name 154.4 is “/j/k.”

FIG. 1C illustrates an exemplary interest group packet 150, in accordance with an embodiment of the present invention. Interest group packet 150 (or interest group 150) at a time of T2 can include basename 152 with a value of “/basename” and member interest names 154.1, 154.3, 154.4, and 154.5. For example, member interest name 154.1 is “/a/b,” member interest name 154.3 is “/e/f,” member interest name 154.4 is “/g/h,” and member interest name 154.4 is “/j/k.” Note that at time T2, member interest name 154.2 has been removed from interest group 150 (as compared to the indicated member interests of interest group 150 at time T1 of FIG. 1B).

FIG. 1D illustrates an exemplary pending interest table 130 maintained by an intermediate node, in accordance with an embodiment of the present invention. PIT 130 reflects a PIT entry added upon receiving interest group 150 at a time of T1 (and determining that no matching content object exists in the CS). An entry in PIT 130 includes a name 132, member interest information 134, and incoming interfaces 146. Member interest information 134 can include a list of tuples comprised of a member interest name 142 and a corresponding member indicator 144. Incoming interfaces 146 can include a list of the interfaces on which the interest corresponding to name 132 has been received (e.g., the arrival interfaces associated with interest group 150). Thus, PIT entry 131.1 can include a name 132 of “/basename,” and a list of member interest information as follows: {/a/b, 0}, {/c/d, 0}, {/e/f, 0}, {/g/h, 0}, {/j/k, 0}. PIT entry 131.1 can also include incoming interfaces 146 with a value of {1, 3, 5}. PIT 130 can also include an entry for a standard interest. For example, PIT entry 131.2 can include a name of “/single/interest1,” member interest information with a null value, and incoming interfaces.

FIG. 1E illustrates an exemplary pending interest table 130 maintained by an intermediate node, in accordance with an embodiment of the present invention. PIT 130 reflects a PIT entry modified upon satisfying a member interest and removing the member interest from interest group 150 at a time of T2. For example, the member interest information for the second listed member interest is updated to reflect that it has been satisfied: {/c/d, 1}.

Note that PIT 130 in FIG. 1D at time T1 reflects an existing PIT entry 131.1 at a receiving node or router. If there is no existing PIT entry corresponding to the interest group base name of “/basename” at time T1, a new PIT entry is added only after the satisfied member interest is removed at time T2. In this case, PIT 130 in FIG. 1E at time T2 only includes member interest information for the remaining member interests, and does not include member interest information for the satisfied member interest (i.e., indicated by the name “/c/d”).

Exemplary Interest Groups and PITs; Decomposition

FIG. 1F illustrates an exemplary interest group packet 160, including information associated with a condition to split the interest group packet, in accordance with an embodiment of the present invention. Interest group packet 160 (or interest group 160) includes the same content as interest group 150 of FIG. 1B at a time of T1, and further includes a hop count 156 with a value equal to “0” and a prefix 158 with a value equal to “.prefix.” A router that receives interest group 160 can determine a condition to decompose the interest group into individual interests, as described below in relation to FIG. 1G. For example, when hop count 156 has a value of zero, a receiving router can determine to decompose the interest group. In addition, when prefix 158 matches a prefix in a receiving router's FIB based on a longest prefix match, the receiving router can also determine to decompose the interest group.

FIG. 1G illustrates exemplary interests 162.1-162.5 created based on splitting the exemplary interest group packet of FIG. 1F, in accordance with an embodiment of the present invention. When the receiving router determines a condition to decompose the interest group, the router can create individual interests with names corresponding to the member interest names of the interest group, at a time of T3. For example, a receiving router can create five separate interests with the following names: interest 162.1 with a name 164.1 of “/a/b”; interest 162.2 with a name 164.2 of “/c/d”; interest 162.3 with a name 164.3 of “/e/f”; interest 162.4 with a name 164.4 of “/g/h”; and interest 162.5 with a name 164.5 of “/j/k.” Interests 162.1-162.5 may be processed under standard CCN rules, as described below in relation to FIG. 4.

FIG. 1H illustrates an exemplary pending interest table 130 maintained by an intermediate node, in accordance with an embodiment of the present invention. PIT 130 includes the same content as PIT 130 of FIG. 1D at a time of T1.

FIG. 1I illustrates an exemplary pending interest table 130 maintained by an intermediate node, in accordance with an embodiment of the present invention. PIT 130 at a time of T3 corresponds to the individual interests created based on the receiving router detecting a decompose condition. PIT 130 at time T3 can include standard PIT entries 172.1-172.5. For example, PIT entry 172.1 can include a name of “/a/b,” member interest information with a null value, and incoming interfaces.

Exemplary Interest Group in ABNF

FIG. 2 presents an exemplary table 200 illustrating an interest group in Augmented Backus-Naur Form (ABNF) notation, in accordance with an embodiment of the present invention. Table 200 includes an interest group 202, which includes a base name, an optional key identification restriction, and a list of interest sets. An interest set 204 can include an optional decompose hop count, an optional decompose prefix, an optional decompose action, and a set of interest lists. A decompose hop count 206 can be an integer, and can indicate a remaining number of hops until the interest set is to be split into one or more individual interests, i.e., split into the individual interests listed in the interest list for interest set 204. A decompose prefix 208 can be a name, and can indicate for a receiving router to split the interest set into one or more individual interests when the prefix matches an entry in a FIB of the router based on a longest prefix match. A decompose action 210 can be a string or command, and can indicate, e.g., “INDIVIDUAL” as the action to take when decompose hop count 206 has a value equal to zero, or when decompose prefix 208 matches a FIB entry in the router. Note that an interest group can include decompose conditions in addition to the ones described herein (e.g., hop count and name prefix). Furthermore, an interest group can include encrypted interest sets that may be re-encrypted, similar to onion encryption.

An interest list 212 can include a set of interests. An interest 214 can include a tuple defined by a name, an optional key identification restriction, and an optional content object hash restriction. A base name 216 can be a name, and a name 218 can be a CCN name, as described herein. A key identification restriction 220 and a content object hash restriction 222 can be a BLOB or other similar value, and a BLOB 224 can be a set of octets.

Intermediate Node Processes Interest Group

FIG. 3A presents a flow chart 300 illustrating a method by an intermediate node for facilitating communication of an interest group packet indicating a collection of interests, in accordance with an embodiment of the present invention. During operation, the system receives, by an intermediate node, a first packet which has a name and indicates a set of member interests, wherein a member interest has a name (operation 302). A name can be a hierarchically structured variable length identifier that includes contiguous name components ordered from a most general level to a most specific level. The first packet can be a manifest. The system performs a lookup in a local cache or content store (CS) for a matching content object based on a name for a respective member interest (operation 304). The system determines whether a matching content object is found in the CS (decision 306). The system can also determine whether it can obtain a matching content object. If no matching content object is found in the CS, the system performs a lookup in the PIT for a matching entry corresponding to the first packet, based on the name for the first packet (operation 308). If a matching entry is not found in the PIT (decision 310), the operation continues as described at Label A of FIG. 3B. If a matching entry is found in the PIT (decision 310), the system adds the arrival interface of the first packet to the matching PIT entry (operation 312) and forwards the first packet (operation 314). Note that a PIT entry can include a name for the first packet, the name for each member interests, and an indicator of whether the member interest is satisfied.

If a matching content object is found in the CS (decision 306), the system removes the member interest from the first packet (operation 320). The system transmits the matching content object on a reverse path (operation 322). The system performs a lookup in the PIT for a matching PIT entry corresponding to the first packet, based on the name for the first packet (operation 324). If a matching entry is not found in the PIT (decision 326), the system determines whether there are any remaining member interests indicated in the first packet (decision 328). If there are no remaining member interests indicated in the first packet, the system discards the first packet (operation 330), and the operation returns. If remaining member interests are indicated in the first packet (decision 328), the operation continues as described at Label A of FIG. 3B. If a matching entry is found in the PIT (decision 326), the operation continues as described at Label B of FIG. 3B.

FIG. 3B presents a flow chart illustrating a method 350 by an intermediate node for facilitating communication of an interest group packet indicating a collection of interests, in accordance with an embodiment of the present invention. From Label A, the system adds an entry in the PIT for the first packet based on the name for the first packet (operation 352). Note that if the operation reaches Label A from decision 326 (matching content object found in CS) instead of decision 310 (no matching content object found in CS), the entry added to the PIT in operation 352 does not include the satisfied member interest. That is, the system has already removed the member interest from the first packet in operation 320. The system also adds the arrival interface to the added PIT entry (operation 354), and forwards the first packet (operation 356).

From Label B, the system marks in the (matching) PIT entry that the member interest is satisfied (operation 354). The system determines whether all member interests in the matching PIT entry are satisfied (decision 364). For example, the system can check an indicator in the matching PIT entry for each of the member interests indicated in the matching PIT entry. Alternatively, the system can check a single indicator which is based on the respective indicators for each of the member interests indicated in the matching PIT entry. Other methods may be used to determine whether a respective member interest in a PIT entry has been satisfied, including setting a flag, a bit, a reserved field, or other method. If all the member interests indicated in the matching PIT entry are satisfied (decision 364), the system removes the matching entry from the PIT (operation 366). If not all of the member interests indicated in the matching PIT entry are satisfied (decision 364), the system adds the arrival interface to the added PIT entry (operation 354), and forwards the first packet (operation 356).

Intermediate Node Processes Interest Group Packet with Decomposition

FIG. 4 presents a flow chart 400 illustrating a method by an intermediate node for facilitating communication of an interest group packet indicating a collection of interests, including detection of information associated with a condition to split the interest group packet, in accordance with an embodiment of the present invention. During operation, the system receives, by an intermediate node, a first packet which has a name and indicates a set of member interests, wherein a member interest has a name (operation 402). The first packet can be a manifest, and the manifest can further indicate a decompose hop count or a decompose prefix. The hop count and the prefix can be associated with the manifest or a set of interests indicated in the manifest. The hop count and the prefix can also be associated with an interest set of an interest group, as described above in relation to FIG. 2. The system determines whether the decompose hop count is equal to zero (decision 404). If the decompose hop count is not equal to zero, the system determines whether the decompose prefix matches a prefix in the FIB based on a longest prefix match method (decision 406). If the prefix has no match in the FIB, the operation continues as described above at operation 304 of FIG. 3A.

If either the decompose hop count is zero (decision 404) or the decompose prefix matches a prefix in the FIB (decision 406), the system can remove the interest set from the interest group (operation 408) (if the hop count or prefix are associated with an interest set of an interest group). The system can split the first packet (manifest) into one or more individual interests, wherein an individual interest has a same name as a respective member interest of the first packet (operation 410). In other words, the system creates a new individual interest for each member interest indicated in the first packet or manifest. The system processes each individual interest under standard CCN rules (operation 412). For example, the system performs a lookup in the CS for a matching content object based on the name for the individual interest. If there is a matching content object, the system forwards the matching content object to a previous-hop node and removes a matching entry from the PIT or removes from the matching PIT entry the arrival interface associated with the individual interest (if there is a matching entry). If there is no matching content object, the system performs a lookup in the PIT for a matching entry. If there is a matching PIT entry, the system adds to the PIT entry the arrival interface associated with the individual interest. If there is no matching PIT entry, the system adds a new PIT entry corresponding to the individual interest. The system also forwards the individual interest.

Upon completing operation 412, the system determines whether there are any remaining member interests indicated in the first packet (decision 414). In some embodiments, if the system removed an interest set from the interest group, the system determines whether there are any interest sets remaining in the interest group. If there are, the system performs decision 414. If there are no remaining member interests indicated in the first packet (or if there are no remaining interest sets in the interest group), the system discards the first packet (operation 416), and the operation returns. If there are remaining member interests indicated in the first packet (decision 414), the operation continues as described at operation 304 of FIG. 3A.

Exemplary Computer and Communication System

FIG. 5 illustrates an exemplary computer and communication system 502 that facilitates communication of an interest group packet indicating a collection of interests, in accordance with an embodiment of the present invention. Computer and communication system 502 includes a processor 604, a memory 506, and a storage device 508. Memory 506 can include a volatile memory (e.g., RAM) that serves as a managed memory, and can be used to store one or more memory pools. Furthermore, computer and communication system 502 can be coupled to a display device 510, a keyboard 512, and a pointing device 514. Storage device 508 can store an operating system 616, a content-processing system 518, and data 532.

Content-processing system 518 can include instructions, which when executed by computer and communication system 502, can cause computer and communication system 502 to perform methods and/or processes described in this disclosure. Specifically, content-processing system 518 may include instructions for receiving, by an intermediate node, a first packet which has a name and indicates a set of member interests, wherein a member interest has a name (communication module 520). Content-processing system 518 can include instructions for, in response to obtaining a content object which satisfies a member interest, removing the indicated member interest from the first packet (packet-managing module 522). Content-processing system 518 can also include instructions for adding an entry in a PIT for the first packet, wherein the entry indicates the name for the first packet, the name for each member interest, and an indicator of whether each member interest is satisfied (PIT-managing module 526). Content-processing system 518 can include instructions for transmitting the first packet to another node (communication module 520).

Content-processing system 518 can further include instructions for processing one or more individual interests (packet-managing module 522). Content-processing system 518 can include instructions for, in response to determining that a hop count is equal to zero (condition-determining module 530): splitting the first packet into the one or more individual interests (group-decomposing module 524); discarding the first packet (packet-managing module 522); and forwarding the one or more individual interests (communication module 520). Content-processing system 518 can additionally include instructions for, in response to determining that a name prefix matches an entry in a forwarding information base based on a longest prefix match (condition-determining module 530): splitting the first packet into the one or more individual interests (group-decomposing module 524); discarding the first packet (packet-managing module 522); and forwarding the one or more individual interests (communication module 520).

Content-processing system 518 can also include instructions for, in response to obtaining a content object that satisfies a member interest (cache-managing module 528): performing a lookup in the PIT for a matching entry corresponding to the first packet (PIT-managing module 526). Content-processing system 518 can include instructions for, in response to obtaining the matching entry (PIT-managing module 526): marking in the matching entry the indicator that the member interest is satisfied (PIT-managing module 526); and, in response to determining that all member interests indicated in the matching entry are satisfied, removing the matching entry from the PIT (PIT-managing module 526). Content-processing system 518 can further include instructions for, in response to not obtaining the matching entry (PIT-managing module 526), and in response to determining that one or more member interests are indicated in the first packet (packet-managing module 522): adding the entry in the PIT for the first packet, wherein the added entry does not indicate the satisfied member interest (PIT-managing module 526); and forwarding the first packet (communication module 520). Content-processing system 518 can include instructions for, in response to determining that no member interests are indicated in the first packet, discarding the first packet (packet-managing module 522).

Content-processing system 518 can additionally include instructions for, in response to not obtaining a content object which satisfies a member interest (cache-managing module 528), performing a lookup in the PIT for a matching entry corresponding to the first packet (PIT-managing module 526). Content-processing system 518 can include instructions for, in response to obtaining the matching entry, marking in the matching entry the indicator that the member interest is satisfied (PIT-managing module 526). Content-processing system 518 can also include instructions for, in response to not obtaining the matching entry, adding the entry in the pending interest table for the first packet (PIT-managing module 526).

Data 532 can include any data that is required as input or that is generated as output by the methods and/or processes described in this disclosure. Specifically, data 532 can store at least: a packet; a name; an interest group or interest group packet; an interest or interest packet; a content object or content object packet; a set of member interests; a packet which has a name and indicates a set of member interests; a hierarchically structured variable length identifier that includes contiguous name components ordered from a most general level to a most specific level; a name for a packet; a name for an interest; a name for a content object; a name for an interest group; a pending interest table (PIT); an entry in a PIT; an indicator of whether a member interest is satisfied; a condition for splitting a packet into one or more individual interests; information associated with a condition for splitting a packet into one or more individual interests; a hop count; a name prefix; a longest prefix match; a forwarding information base (FIB); a local cache or a content store (CS); and an arrival interface associated with an interest; a lookup in a PIT or CS.

The data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. The computer-readable storage medium includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing computer-readable media now known or later developed.

The methods and processes described in the detailed description section can be embodied as code and/or data, which can be stored in a computer-readable storage medium as described above. When a computer system reads and executes the code and/or data stored on the computer-readable storage medium, the computer system performs the methods and processes embodied as data structures and code and stored within the computer-readable storage medium.

Furthermore, the methods and processes described above can be included in hardware modules or apparatus. The hardware modules or apparatus can include, but are not limited to, application-specific integrated circuit (ASIC) chips, field-programmable gate arrays (FPGAs), dedicated or shared processors that execute a particular software module or a piece of code at a particular time, and other programmable-logic devices now known or later developed. When the hardware modules or apparatus are activated, they perform the methods and processes included within them.

The foregoing descriptions of embodiments of the present invention have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present invention. The scope of the present invention is defined by the appended claims. 

What is claimed is:
 1. A computer-implemented method for forwarding packets, the method comprising: receiving, by an intermediate node, a first packet which has a name and indicates a set of member interests respectively requesting content objects to satisfy the member interests, wherein each member interest has a name that is a hierarchically structured variable length identifier including contiguous name components ordered from a most general level to a most specific level; in response to obtaining a particular content object, removing the member interest requesting the particular content object from the first packet; adding an entry in a pending interest table for the first packet, wherein the entry indicates the name for the first packet, the name for each member interest, and a set of indicators respectively indicating which of the member interests are satisfied; and after removing the member interest requesting the particular content object from the first packet, transmitting the first packet to another node, thereby facilitating efficient communication of the set of member interests indicated in the first packet.
 2. The method of claim 1, wherein the first packet further includes information associated with a condition for splitting the first packet into one or more individual interests respectively corresponding to one or more member interests of the set of member interests, wherein each individual interest has the same name as the respective corresponding member interest, wherein the method further comprises: processing the one or more individual interests.
 3. The method of claim 2, wherein the information associated with the condition includes a hop count which indicates a number of remaining hops until the first packet is to be split into the one or more individual interests, wherein the method further comprises: in response to determining that the hop count is equal to zero: splitting the first packet into the one or more individual interests; discarding the first packet; and forwarding the one or more individual interests.
 4. The method of claim 2, wherein the information associated with the condition includes a name prefix, wherein the method further comprises: in response to determining that the name prefix matches an entry in a forwarding information base based on a longest prefix match: splitting the first packet into the one or more individual interests; discarding the first packet; and forwarding the one or more individual interests.
 5. The method of claim 2, wherein processing the one or more individual interests further comprises: performing one or more lookups in a cache for one or more content objects to satisfy the one or more individual interests based on a name for the one or more individual interests; in response to obtaining the one or more content objects to satisfy the one or more individual interests: forwarding the one or more content objects to satisfy the one or more individual interests to a previous-hop node; and removing from the pending interest table one or more matching entries corresponding to the one or more individual interests, or removing from the one or more matching entries an arrival interface associated with the one or more individual interests; and in response to not obtaining the one or more content objects to satisfy the one or more individual interests: performing one or more lookups in the pending interest table for the one or more matching entries corresponding to the one or more individual interests; in response to obtaining the one or more matching entries, adding to the one or more matching entries the arrival interface associated with the one or more individual interests; in response to not obtaining the one or more matching entries, adding one or more new matching entries corresponding to the one or more individual interests; and forwarding the one or more individual interests.
 6. The method of claim 1, wherein in response to obtaining the particular content object, the method further comprises: performing a lookup in the pending interest table for a matching entry corresponding to the first packet; in response to obtaining the matching entry: marking in the matching entry the indicator that the member interest requesting the particular content object is satisfied; and in response to determining that all member interests of the set of member interests indicated in the matching entry are satisfied, removing the matching entry from the pending interest table; and in response to not obtaining the matching entry: in response to determining that one or more other member interests of the set of member interests are indicated in the first packet, adding a new matching entry in the pending interest table, wherein the new matching entry does not indicate the member interest requesting the particular content object; and in response to determining that no other member interests of the set of member interests are indicated in the first packet, discarding the first packet.
 7. The method of claim 1, further comprising: in response to not obtaining the particular content object, performing a lookup in the pending interest table for a matching entry corresponding to the first packet; in response to obtaining the matching entry, marking in the matching entry the indicator that the member interest requesting the particular content object is satisfied; and in response to not obtaining the matching entry, adding a new matching entry in the pending interest table for the first packet.
 8. A computer system for facilitating forwarding of packets, the system comprising: a processor; and a storage device storing instructions that when executed by the processor cause the processor to perform a method, the method comprising: receiving, by an intermediate node, a first packet which has a name and indicates a set of member interests respectively requesting content objects to satisfy the member interests, wherein each member interest has a name that is a hierarchically structured variable length identifier including contiguous name components ordered from a most general level to a most specific level; in response to obtaining a particular content object, removing the member interest requesting the particular content object from the first packet; adding an entry in a pending interest table for the first packet, wherein the entry indicates the name for the first packet, the name for each member interest, and a set of indicators respectively indicating which of the member interests are satisfied; and after removing the member interest requesting the particular content object from the first packet, transmitting the first packet to another node, thereby facilitating efficient communication of the set of member interests indicated in the first packet.
 9. The computer system of claim 8, wherein the first packet further includes information associated with a condition for splitting the first packet into one or more individual interests respectively corresponding to one or more member interests of the set of member interests, wherein each individual interest has the same name as the respective corresponding member interest, wherein the method further comprises: processing the one or more individual interests.
 10. The computer system of claim 9, wherein the information associated with the condition includes a hop count which indicates a number of remaining hops until the first packet is to be split into the one or more individual interests, wherein the method further comprises: in response to determining that the hop count is equal to zero: splitting the first packet into the one or more individual interests; discarding the first packet; and forwarding the one or more individual interests.
 11. The computer system of claim 9, wherein the information associated with the condition includes a name prefix, wherein the method further comprises: in response to determining that the name prefix matches an entry in a forwarding information base based on a longest prefix match: splitting the first packet into the one or more individual interests; discarding the first packet; and forwarding the one or more individual interests.
 12. The computer system of claim 9, wherein processing the one or more individual interests further comprises: performing one or more lookups in a cache for one or more content objects to satisfy the one or more individual interests based on a name for the one or more individual interests; in response to obtaining the one or more content objects to satisfy the one or more individual interests: forwarding the one or more content objects to satisfy the one or more individual interests to a previous-hop node; and removing from the pending interest table one or more matching entries corresponding to the one or more individual interests, or removing from the one or more matching entries an arrival interface associated with the one or more individual interests; and in response to not obtaining the one or more content objects to satisfy the one or more individual interests: performing one or more lookups in the pending interest table for the one or more matching entries corresponding to the one or more individual interests; in response to obtaining the one or more matching entries, adding to the one or more matching entries the arrival interface associated with the one or more individual interests; in response to not obtaining the one or more matching entries, adding one or more new matching entries corresponding to the one or more individual interests; and forwarding the one or more individual interests.
 13. The computer system of claim 8, wherein in response to obtaining the particular content object, the method further comprises: performing a lookup in the pending interest table for a matching entry corresponding to the first packet; in response to obtaining the matching entry: marking in the matching entry the indicator that the member interest requesting the particular content object is satisfied; and in response to determining that all member interests of the set of member interests indicated in the matching entry are satisfied, removing the matching entry from the pending interest table; and in response to not obtaining the matching entry: in response to determining that one or more other member interests of the set of member interests are indicated in the first packet, adding a new matching entry in the pending interest table, wherein the new matching entry does not indicate the member interest requesting the particular content object; and in response to determining that no other member interests of the set of member interests are indicated in the first packet, discarding the first packet.
 14. The computer system of claim 8, wherein the method further comprises: in response to not obtaining the particular content object, performing a lookup in the pending interest table for a matching entry corresponding to the first packet; in response to obtaining the matching entry, marking in the matching entry the indicator that the member interest requesting the particular content object is satisfied; and in response to not obtaining the matching entry, adding a new matching entry in the pending interest table for the first packet.
 15. A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method, the method comprising: receiving, by an intermediate node, a first packet which has a name and indicates a set of member interests respectively requesting content objects to satisfy the member interests, wherein each member interest has a name that is a hierarchically structured variable length identifier including contiguous name components ordered from a most general level to a most specific level; in response to obtaining a particular content object, removing the member interest requesting the particular content object from the first packet; adding an entry in a pending interest table for the first packet, wherein the entry indicates the name for the first packet, the name for each member interest, and a set of indicators respectively indicating which of the member interests are satisfied; and after removing the member interest requesting the particular content object from the first packet, transmitting the first packet to another node, thereby facilitating efficient communication of the set of member interests indicated in the first packet.
 16. The storage medium of claim 15, wherein the first packet further includes information associated with a condition for splitting the first packet into one or more individual interests respectively corresponding to one or more member interests of the set of member interests, wherein each individual interest has the same name as the respective corresponding member interest, wherein the method further comprises: processing the one or more individual interests.
 17. The storage medium of claim 16, wherein the information associated with the condition includes a hop count which indicates a number of remaining hops until the first packet is to be split into the one or more individual interests, wherein the method further comprises: in response to determining that the hop count is equal to zero: splitting the first packet into the one or more individual interests; discarding the first packet; and forwarding the one or more individual interests.
 18. The storage medium of claim 16, wherein the information associated with the condition includes a name prefix, wherein the method further comprises: in response to determining that the name prefix matches an entry in a forwarding information base based on a longest prefix match: splitting the first packet into the one or more individual interests; discarding the first packet; and forwarding the one or more individual interests.
 19. The storage medium of claim 15, wherein in response to obtaining the particular content object, the method further comprises: performing a lookup in the pending interest table for a matching entry corresponding to the first packet; in response to obtaining the matching entry: marking in the matching entry the indicator that the member interest requesting the particular content object is satisfied; and in response to determining that all member interests of the set of member interests indicated in the matching entry are satisfied, removing the matching entry from the pending interest table; and in response to not obtaining the matching entry: in response to determining that one or more other member interests of the set of member interests are indicated in the first packet, adding a new matching entry in the pending interest table, wherein the new matching entry does not indicate the member interest requesting the particular content object; and in response to determining that no other member interests of the set of member interests are indicated in the first packet, discarding the first packet.
 20. The storage medium of claim 15, wherein the method further comprises: in response to not obtaining the particular content object, performing a lookup in the pending interest table for a matching entry corresponding to the first packet; in response to obtaining the matching entry, marking in the matching entry the indicator that the member interest requesting the particular content object is satisfied; and in response to not obtaining the matching entry, adding a new matching entry in the pending interest table for the first packet. 